Moved nsInterfaceInfoManager files from the libxpt directory (where
they would have precipitated an unpleasant circular dependency between
xpidl and nsISupports.h) into a new subdirectory.
Added corresponding entries to allmakefiles.sh.
nsInterfaceInfoManager is intended to abstract the loading and
management of typelib information generated by xpidl, for use by
xpconnect.
Sanitized the GTK nsDeviceContextSpecFactoryG, nsRenderingContextPS, nsDeviceContextPS,
and nsDeviceContextSpecG by removing WIN32 dependencies.
Added checks for null widgets in nsWidget and nsScrollbar GTK implementations.
